Development and validation of the Nearshore Wave Prediction System

The National Weather Service's (NWS) National Centers for Environmental Prediction (NCEP) currently produces coastal wave guidance products at a resolution of 4 arc-minutes. However, the demand for high-resolution nearshore forecast products has been steadily increasing over the past decade. The Nearshore Wave Prediction System (NWPS) is currently being developed to address this need. This system is conceived to provide on-demand, high-resolution nearshore wave model guidance to forecasters. It is designed to run locally at Weather Forecast Offices, and is driven by forecaster-developed wind grids and offshore wave boundary conditions from NCEP's operational WAVEWATCH III. In addition, current fields from NCEP's Real-Time Ocean Forecast System (RTOFS) and water level fields from the National Ocean Service's (NOS) Extratropical Surge and Tide Operational Forecast System (ESTOFS) are applied. The nested nearshore wave model used is SWAN, with a new nearshore version of WAVEWATCH III as alternative. NWPS is based on the IFP-SWAN and SR-SWAN guidance systems previously developed by the NWS Western and Southern Regions, respectively. It consolidates these earlier systems by baselining their functionality into the new Advanced Weather Information Processing System (AWIPS) II and extends them on a number of fronts. These include the optimization of wave model settings, and the refinement of wave partitioning and spatial and temporal tracking algorithms. The proposed system has been calibrated and subsequently validated for a number of tropical and extratropical storms along the U.S. coast. Comparisons with observations show good agreement. This paper presents a description of the system and its functionality, along with results of the aforementioned calibration, validation, and sensitivity tests.